(This paper was presented at the
"International Conference on Increasing Livestock Production
through Utilization of Local Resource". CECAT, Beijing,
18.22 October 1993)

Summary

The use of multipurpose animals for milk meat and draught, has
shown potential for increasing farm productivity and income.
Females used for draught require better quality feed and
management than oxen or dry cows. Despite the requirement for
higher quality feed, there is potential for saving feed resources
overall because fewer animals are needed to supply total farm
work and milk needs. Research has shown that conception and milk
production of cattle and buffaloes are affected if diets based on
crop residues or low quality hays are not improved or
supplemented, especially when working periods coincide with
lactation. Our research showed that hay (~7.0 MJ ME/kg DM) intake
was 10% greater in working compared to non.working cows. Cows
responded to underfeeding by a progressive adaptation until a new
equilibrium between dietary supply and requirements was reached.
However, in draught cows fed low quality roughage, the
"work.induced" increased dry matter intake was not
sufficient to cover all energy requirements for work and/or milk.
While inadequate feeding may not affect work output, high rates
of body weight loss lead to decreased milk production and
reproductive ability. Total milk production in a two.year period
was similar for working and non.working cows (1985 vs.
2225 kg). Work had a minimal affect on milk production when
nutrition was adequate for lactation and work. Roughage diets
with less than 8 MJ ME/kg DM could not support potential
reproductive ability of draught cows. Supplementation improved
reproductive performance of working cows and by 365 days
post.partum, conception rate of non working.supplemented and of
working.supplemented cows was similar. However, in working cows,
conception was delayed by about 120 days. Body condition at
calving significantly affected post.partum reproductive ability
of cows. Many more site.specific investigations need to be
carried out to find the most economic combinations of feeds
throughout the year and to relate food quality and intake to
animal performance, especially in early lactation when the high
energy demand for lactation could be associated with work energy
needs.

Where animal traction is currently used, the major sources of
fodder are crop residues, conserved forage and browse. The
intensification of agriculture leaves fewer and fewer
opportunities for animals to graze, and feed resources that are
alternative to "conventiona"' grazing are becoming
increasingly important (Mathers and Otchere 1993).

Energy expenditure and feed intake

In animals used for draught, maintenance and work energy are
quantitatively the most important. Apart from extra net energy
for work, draught animals also require more energy for
maintenance than non.working animals. Work by Lawrence et al
(1989a,b) shows an increase of about 10% in net energy for
maintenance of working oxen fed poor quality diets.

Even though it is now possible to define many of the energy
expenditures of draught animals reasonably well, there are still
difficulties in estimating the metabolizable energy content of
many tropical feeds and in predicting the voluntary intake of low
quality roughages necessary to provide the metabolizable energy
to meet these requirements (Lawrence 1987).

The main factor which determines intake is food quality, but
other factors, such as ambient temperature and physiological
state of the animal are also important. Even though published
data have shown a strong relationship between DM intake and
production responses, it has been difficult to establish cause
and effect. Weston (1985) suggested that increased energy demand
by an animal would result in increased feed intake. While this is
true in lactating cows, results of studies on the effect of work
on feed intake are inconsistent. Winugroho (1993) indicated that
one of the causes of this inconsistency could be attributed to
the different efficiency with which available energy is used
which depends on the supply of nutrients (feed, body reserves)
and on the intensity of work. In working animals, increased heat
load and decreased gut motility and rate of passage may reduce
appetite and intake (Young 1985). Thus, a major increase in feed
intake in working animals exposed to heat stress from work and
from the environment will be difficult to achieve. This would be
particularly true in Buffalo, which have a much poorer heat
dissipating capacity than cattle.

In studies cited by Mathers and Otchere (1993), there was an
increase in food intake during work in six of the cases; in four
studies, there was a decrease. In most cases, however, the
difference was not statistically significant. Henning (1987)
reports that the difference between energy demand and energy
supply per se is not the major factor in increasing feed intake.
In the study reported, feed intake did not increase as a result
of increased energy expenditure through walking exercise.
Similarly, Bamualim et al (1987) showed no significant
differences between working and non.working animals in their feed
intake and digestibility, in contrast to previous findings by
Ffoulkes and Baumalim (1986) who reported increases in both feed
intake and digestibility in buffalo after 3 weeks of work.
Matthewman et al (1989) indicated that exercise did not
affect dry matter intake of cows.

Based on observations of the nutritional status of working
animals, it is suggested that in areas with available roughages
containing more than 9 MJ of ME/kg DM, feeding of draught animals
should be adequate (ARC 1980; Lawrence 1987). However, many
unsupplemented and unmodified tropical forages do not contain
that concentration of energy and would be incapable of supporting
intakes up to twice maintenance. Feeds which are normally fed to
working cattle and buffalo are fibrous roughages and their ME
content varies from 6 to 8 MJ/kg DM. Therefore, liveweight losses
in animals eating these diets during the work season would be
expected. Greater energy deficit would occur if the working
animals would be lactating and/or pregnant (Teleni 1993).

Even under conditions where adequate feed supplementation is
not available to maintain body weight, animals can still
satisfactorily perform work by drawing on body reserves. The
length of time such a situation can effectively exist will depend
on the previous condition of the draught animal, the amount of
work being done and its duration (Goe 1987).

Even though draught animals should be in good condition
especially at the beginning of the working periods, work
conducted by Khibe and Bartolomew (1993) in Mali shows that
feeding for weight maintenance during the dry season would
represent an inefficient use of feed resources compared with
short term feeding during the working period. Although animals
had lost an average of 50 kg during the dry season, there was no
evidence of any effect of liveweight or body condition on work
output in observations made during the cropping season.
Therefore, the economic trade.offs between loss of body
condition, work output and costs of feeding supplements during
and before the working season should be examined in detail. This
issue becomes more complex with working cows which need to
maintain body weight after parturition in order to conceive
(Zerbini et al 1993).

Utilization of crop residues and browse

A knowledge of the energy requirements of draught animals
enables rations to be formulated from any feeds which are
available provided their metabolizable energy contents are known.
Research tends to focus on how best to make use of the limited
feed available and on ways of supplementing or treating feeds to
improve their quality (Lawrence and Zerbini 1993). Experiments by
Chiadet (1989), quoted by Lawrence and Zerbini (1993), used 4
pairs of buffaloes to test 4 different diets. The untreated diet
consisted of rice straw and fresh grass, and in the others, the
rice straw was replaced by urea.treated rice straw and/or a
concentrate ration. All 3 improved diets resulted in a 7%
increase in ploughing capacity, in increased weight gain during
rest periods and a diminution in weight loss when the animals
worked.

Combinations of urea and concentrate (cotton seed cake) were
also used by Khibe and Bartholomew (1993) to improve a basal diet
of "bush hay" fed to working oxen. Animals receiving
untreated hay or hay + urea gained on average 20 kg during the
trial and those receiving hay + urea + concentrate gained 40 kg.
The work required of the animals was relatively low and no
difference in work performance was noted between the groups.
However, the improvement associated with the cotton seed cake may
have been due as much to the supplementary metabolizable energy
provided as to the supplementary protein. In another study,
working oxen receiving only rice straw lost 10 kg liveweight on
average during the trial whereas those receiving a supplement of
4 kg/day of fodder tree Ficus Auriculata (21.6% N x 6.25)
made minimal gains (Pearson 1991).

The diversity of products that have been used as feeds or
supplements for draught animals indicate the need for
site.specific research to ensure their efficient utilization.

Nutrition of multipurpose draught animals

Animals are seldom kept exclusively for draught; they are
often trying to grow or lactate at the same time. Much recent
research has focused on the partition of nutrients in the animal
between these various functions and the best ways of formulating
diets to meet nutrient needs.

The opportunity costs for farms that maintain oxen primarily
for land cultivation are considerable and are likely to become
greater as human and livestock pressure on land increases.
Draught oxen also compete with cows and associated stocks for
normally limited supplies of foodstuffs. The use of crossbred
dairy cows for the dual purpose of milk production and draught is
one possible means of alleviating this situation, especially in
areas where dairy production schemes are being implemented in
mixed cereal.livestock farming systems (Gryssels and Anderson
1985). In many tropical farming systems, the preferred draught
animals are oxen, but cows are used where available land and feed
for cattle are scarce. For instance in Bangladesh, Indonesia, Sri
Lanka, and Senegal between 25 and 50% of draught animals are
cows. However, other situations exist where land and population
pressure associated with inefficient use of draught oxen is
critical to crop production (Matthewman et al 1990).
Draught cows are used primarily where feed resources for draught
animals are scarce. However, feed shortage is not the only factor
governing the choice between using oxen or cows. Other factors
include: shortage of males, human population pressure,
sub.division of holdings, and shortage of capital (Jabbar 1983).

Draught cows have higher nutrient requirements than oxen
especially if they have to perform draught work during the early
stages of lactation when nutrient supply has to cover the needs
for work, lactation, and reproductive activity. Therefore it is
especially important that cows to be used for draught be in
reasonable body condition all year round. This will allow them to
sustain all functions required without undue loss of body weight
and a limited effect on milk yield and reproductive performance.
Supplementary feeding may be necessary unless good quality forage
is available all year round.

Uncertainty exists at the present time about the exact effect
of work on milk production and, while some authors consider that
well fed cows suffer no adverse effects from working, it would
appear that milk yields and fertility are affected in poorly fed
animals.

Matthewman (1990) indicated that dairy cows using
approximately 12 MJ ME per day for work showed a reduction of
milk production between 7 and 14% depending on diet. However,
milk yield declined on walking days and recovered to almost
non.walking levels on the intervening non.walking days. The daily
yield of milk fat, protein and lactose were not affected by
exercise. Body weight change was similar. The author concluded
that the amount of exercise done by the cows would not have any
long term effects on lactation performance.

Energy metabolism and partition in dairy cows used for draught
There is a need to quantify the energy partition to different
functions by the working.lactating.conceiving cow. How body
reserves contribute to energy expenditure of working cows is not
known satisfactorily and there appears to be no direct
information on the extent to which work might influence the
composition of gain or loss. The need for the animal to regain
body weight during the non working season is a further feature of
draught animal management.

There is a general consensus that free fatty acids and glucose
are the nutrients preferentially used by muscles of working
animals (Teleni and Hogan 1989). Glucose and NEFA are key players
in the energy metabolism of lactating cows. Glucose is not only a
major substrate for lactose synthesis, but also an essential
energy substrate for reproductive activity (Gaines 1989; Butler
and Smith 1989; Harrison 1982). Fatty acids are precursors of
milk fat, but also seem to influence neuroendocrine activities
regulating the synthesis and release of reproductive hormones
(Shillo 1992). Thus, a strong competition for these metabolites
could occur when cows are lactating and working during the same
period. Intermediate metabolites of carbohydrate and lipid
metabolism such as lactate and ketone bodies would also play an
important role in the overall energy partition strategy in the
lactating working cow. The specific effect of work on energy
metabolites must be an important factor in evaluating the overall
efficiency of cows used for draught.

Work carried out at the International Livestock Centre for
Africa (ILCA 1990) has shown that non.supplemented cows seemed to
have partitioned the available energy towards maintenance and
work, penalizing milk production and reproduction. Among
supplemented cows, those working exhibited only a greater
postpartum interval from calving to conception. It is not known
whether it was a direct effect of work per se or a deficit of
energy yielding substrates, in particular during working periods.

Data from the ILCA/IAR cow traction research project (Zerbini etal, unpublished) show that plasma glucose was greater in
supplemented than in non.supplemented cows in both working and
non. working cows (8 to 16%). Working cows had lower plasma
glucose after working hours than non.working cows (.16%). NEFA
was higher in working cows at the end of working hours and after
the rest hour between working hours. This effect was greater in
non.supplemented than in supplemented cows. The rise of plasma
NEFA of about 150% in working cows during working hours is in
agreement with the results of Hambitzer and Bent (1988) which
showed that free fatty acids increased 7.fold in exercised Arab
horses. Similarly, Teleni et al (1989) reported an increase in
glucose entry rate of approximately 84% and an increase in FFA
entry rate of approximately 150% in working cattle. In the
pregnant and/or lactating working cows or buffaloes the increased
entry rate of glucose could be accounted for by the gravid uterus
or the mammary gland uptake. In our study, plasma glucose and
NEFA showed a negative linear relationship in
non.working/supplemented, working/non.supplemented and working/
supplemented cows. The decrease of plasma glucose and the
increase in NEFA during work indicates a declining utilization of
glucose and an increasing use of NEFA by muscle during
consecutive working hours. Working/supplemented cows might have
used dietary fat and fat and carbohydrate stores in muscle to a
larger degree than working/non.supplemented cows.

The results of this study and those reported by Zerbini et
al (1993) for the same cows, suggest that an average decrease
of plasma glucose from 55.5 to 50.0 mg/dl over all sampling times
could be related to a decrease of the probability of conception
by a factor of 4 in non.supplemented compared to supplemented
cows. On the other hand, an average reduction of plasma glucose
from 54.9 to 46.0 mg/dl, and an increase of NEFA of 146% in
working cows during working hours could be related to a decrease
of the probability of conception by a factor of 2 for both diets.
Similarly, the lower plasma glucose of non.supplemented cows
compared to supplemented cows relates well with the effect of
diet supplementation on milk yield reported by Zerbini et al
(1992) with the same cows. Milk production over one.year period
was reduced by 53% in non. supplemented cows. During the same
period the effect of work was not significant.

Energy requirements of the working cow

When cows are used for work, the additional energy requirement
for work must be added to maintenance and milk production (Table
1).

Table 1: Calculated
daily energy requirements of crossbred cows*

Work output =
2.7 MJ/day; body weight = 420kg,

Milk yield =
4.8 kg/d.

WORK OUTPUT

2.7 MJ

NET ENERGY
FOR WORK

9.0 MJ

NET ENERGY
FOR WALK

5.0 MJ

NET ENERGY
FOR WORK + WALK

14.0 MJ

ME FOR WORK +
WALK

20.9 MJ

ME
MAINTENANCE (*)

43.6 MJ

NET ENERGY
MILK/kg (*)

3.1 MJ

ME MILK (4.8
kg/d)

25.4 MJ

ME GESTATION
(*)

8.2 MJ

TOTAL ENERGY
REQUIREMENT (ME)

98.1 MJ

(*) Feeding Standards for Australian Livestock 1990)

At the end of the first working period after calving (90
days), hay dry matter intake of non supplemented.working cows
increased by 1.6 kg/day compared to non supplemented.non working
cows, equivalent to 12 MJ ME associated with a body weight loss
of 0.39 kg/day which equates approximately to 14.4 MJ ME. The
total output was there fore 26.4 MJ ME per day. Since the total
energy requirements of working cows are 98.1 MJ/d they would
suffer a deficit of 12.1 MJ/day which would affect milk yield and
body weight considerably. Non working cows showed a deficit of
only 5.3 MJ per day.

Production and reproduction performance of
crossbred dairy cows used for draught

The following results show the effect of work and diet
supplementation on diet apparent digestibility, dry matter
intake, milk production and body weight change over a period of
two years. This period included 200 days of work.

Feed intake, feed utilization and work output

Table 2 shows preliminary results of in vivo
digestibility of organic matter and calculated ME content of hay
and supplemented diets comparing non working cows and working
cows during a working period. Supplementation increased organic
matter digestibility by 4.4 % units in non working cows and by
3.3 % units in working cows. The digestible organic matter in
feed dry matter was greater for supplemented cows but differences
were not as significant as for organic matter digestibility.
Calculated metabolizable energy reflect the greater value of the
supplemented diet, but also the greater feed utilization of
working compared to non working cows. Similarly, Ffoulkes and
Baumalim (1989) reported that work increased the availability of
feed energy in buffalo.

Tables 3 and 4 show that over one and two year periods, total
hay dry matter intake was greater for working than non working
cows and for supplemented than non.supplemented cows.
Supplemented cows consumed more dry matter than non.supplemented
cows. Total dry matter intake followed a similar pattern. Results
indicate that working cows increased dry matter intake compared
to non working cows to sustain milk production and/or support
energy expenditure for work. Of particular practical importance
is the increased hay dry matter intake of non.supplemented
working cows. Ruminants respond to underfeeding by a progressive
adaptation until a new equilibrium between dietary supply and
requirements is reached. Cows in our study increased dry matter
intake to partly support greater energy demands for work.
However, as indicated by Ortiguez (1991), there might be a drop
in maintenance energy requirements originating from a decrease in
basal metabolism that depends on the level and duration of
undernutrition. If this could be the case for non working cows,
it probably would not hold for working cows which increased dry
matter intake, thus increasing digestive tract metabolism. A
desirable trait of the lactating working cows would be a large
food intake capacity. Larger animals could be of considerable
advantage in situations where high fibre roughages are utilized.
Larger animals are more efficient chewers and spend less time
chewing per kg of ingested cell wall constituents. Statistically,
body size accounts for 52% of variation in intake (Bae et al
1983).

Table 3: Work
output, dry matter intake, milk yield and body weight
change of F1 crossbred dairy cows used for draught over a
period of 365 days.

Intake

Intake

Milk

Bodyweight

Hay

DM

yield

change

(kg)

(kg)

(kg)

(kg)

NW.NS

2559

2559

860

.59.8

NW.S

2950

3755

1764

9.4

W.NS

3020

3020

801

.61.0

W.S

3207

4139

1756

25.2

ąSE

141

150

9.1

Work

Supp

P<.05

P.001

P<.001

P<.001

* P < 0.05 ** P < 0.01 *** P < 0.001

Table 4: Work
output, dry matter intake, milk yield and body weight
change of F1 crossbred dairy cows used for draught over a
period of 730 days.

Intake

Intake

Milk

Bodyweight

Hay

DM

yield

change

(kg)

(kg)

(kg)

(kg)

NW.NS

5164

5164

1263

.70.0

NW.S

5676

7093

2186

.12.4

W.NS

6055

6055

927

.85.6

W.S

6358

7957

3044

.23.4

ąSE

241

216

9.1

Work

P<.001

P<.001

NS

NS

Supp

P.05

P<.001

P<.001

P<.001

Work output of supplemented and non.supplemented cows was
similar in the first and second year periods (260 vs. 270
and 229 vs. 248 MJ, respectively).

Lactation

During the first year, the effect of work on average daily
milk yield was not significant even though milk yield was reduced
by work during the first working period (90 days). However, over
both years, total milk production was similar for working and
non. working cows. Supplemented cows produced significantly more
milk than non.supplemented cows (Table 3 and 4).

Non.supplemented cows lost body weight throughout the two.year
period. Supplemented cows, except for working cows during the
first and last working periods (90 and 540 days), maintained
initial body weight. Total body weight losses were similar for
working and non.working cows (Table 3 and 4). Total body weight
change of non.supplemented cows was significantly greater than
that of supplemented cows. Similar body weight losses in working
and non.working cows and minimal body weight loss of supplemented
working cows compared to non.supplemented working cows indicated
that the "work.induced" increased hay dry matter intake
in non. supplemented working cows was insufficient to cover all
energy requirements. Thus, non supplemented cows continued to
loose body weight and stopped milk production and reproduction
functions as a result of work. On the other hand, supplemented
working cows were able to work and produce milk without adverse
effect on body weight.

Table 5: Numbers
of cows which showed oestrus or conceived by 365 days and
median intervals from calving to conception

Oestrus

Conception

Median

Median

interval

interval

Treatment

n

n

(days)

n

(days)

S.NW

10

10

76

10

76

S.W

10

10

198

9

227

NS.NW

10

10

153

6

251

NS.W

10

2

NA

2

NA

All

40

28

211

27

235

Source: Zerbini et al 1993

Reproduction

Body weight losses greater than 15% have been reported to
impair ovarian activity in female buffaloes (Teleni et al 1989).
Work carried out in early lactation could delay return to
oestrus. Reduced blood sugar levels resulting from work could
affect implantation if work is carried out at this time. Reducing
body weight loss from 0.7 to 0.3 kg/day with supplementary
feeding has been shown to improve reproductive performance by
about 65% (ILCA 1990). Table 5 shows the effect of work and diet
supplementation on conception rate of cows used for draught. In
supplemented cows, work significantly delayed days to conception
(Zerbini et al 1993). However, by 365 days post.partum,
conception rate was similar for supplemented.working cows and
supplemented.non working cows. Body condition at calving
significantly affected post.partum reproductive ability of non
working and working cows. The incidence of ovulation without
estrus was higher in working than in non. working cows and in non
supplemented than in supplemented cows. Even though in working
cows diet supplementation offset the negative effect of work on
the onset of estrus and conception, a relatively higher number of
cows in the supplemented working group had ovulations without
estrus before a normal estrus cycle was established (Zerbini et
al 1993).

Natural grass hay alone could not support potential
reproductive ability of crossbred cows. Work output of
supplemented cows might be associated with longer calving
intervals. The economic trade.offs between longer calving
intervals and work output should be examined in detail.

It is unlikely that the cessation of cyclic activity in
working cows was a result of direct competition for nutrients
between the ovary and other tissues. It is possible that the
depletion of body reserve nutrients to certain critical levels
had signalled metabolic controls to switch off non vital
processes such as ovarian function. A clear definition of body
weight and condition at the start of the work season and rate of
weight loss which are compatible with normal ovarian activity is
desirable, as well as the effect of interaction between work and
body reserve nutrients on cyclic activities in cattle and
buffaloes. Work did not influence conception rate in supplemented
cows, but had a substantial influence in non.supplemented cows.
The availability of nutrients, particularly, energy and protein,
is often a limiting factor for production in cows fed crop by
products. Nutritional constraints combined with draught work
activities could cause a loss in body condition and lead to
postpartum anestrus (Jainudeen, 1985). Therefore, specific
intervention options on the amount of work and/or feeding regimes
sufficient to induce behavioral estrus during the early
postpartum period need to be established.

The significant effect of body condition at calving on onset
of oestrus and conception, indicates the importance of the
partition of body energy stores and feed energy for different
physiological functions when cows are simultaneously working and
lactating. Future research should include defining priorities of
nutrient partition in lactating and/or pregnant working females.
Detailed physiological studies on post.partum reproductive
functions in relation to hormonal changes, nutrition, work and
their interaction, is warranted.

Economic appraisal of effect of work and diet Partial
budgeting analysis was used in the economic assessment of effects
of work and diet supplementation on dairy cows on.station. Table
6 shows that regardless of work treatment, gross margin from
supplemented cows was much higher than from non supplemented cows
which in fact resulted in negative gross margin. The higher feed
costs, and lower value for milk and calves of working cows were
largely offset by work output value, resulting in higher gross
margin for working cows.

This comparison shows the economic viability and the
sustainability of the supplemented.working treatment and
demonstrates that adequate feeding is a major factor determining
the profitability of the introduction of crossbred cows into the
farming system, independently of their use for draught work or
not (Zerbini and Getachew Asamenew 1991). In addition, non
adequate feeding makes the introduction of crossbred cows not a
sustainable option because cows not supplemented result in lower
calf output and eventually in a complete stop of reproductive
functions (Zerbini et al 1993) with loss of production and
cow value.

Conclusions

Multipurpose cows could play an important role as dual purpose
animals in many ecoregions where smallholder farming systems are
established. In particular, their preference over oxen could
contribute to a better utilization of feed resources that are
already scarce. In addition, the use of cows for draught would
allow for males to be fattened and sold younger and to a greater
security of replacements. More productive animals on farm could
allow for a reduction of stocking rate and overgrazing, thus
contributing to the establishment of a more stable soil system.
However, a reduction of herd size by using crossbred cows for
traction will depend primarily on the available supply of
crossbred animals and farmers access to suitable feeds and
veterinary services. For feeding practices, two possible
solutions may be recommended where crossbred cows are used for
draught:

(i) Production and feeding of improved forages
(grasses+legumes, legumes, or MPT) to increase digestibility and
energy intake of cows to levels which would allow them to support
both milk production, reproduction, and work with acceptable
physiological body weight loss.

(ii) Feeding of improved quality crop residues and production
of well managed natural pasture hays associated with concentrate
feeding during early lactation, especially if cows are due to
work during that period.

Application of new techniques and research findings for better
utilization of crop by.products and conservation of the natural
forage during particular periods of the year needs particular
attention.

Gryssels G and F M Anderson 1985 Use of
crossbred dairy cows as draught animals: experience from the
Ethiopian Highlands. In: Research Methodology for Livestock on
Farm Trials. Proceedingsof a workshop held March 25.28 at Aleppo,
Syria. International Development Research Centre, Ottawa.
p237.258

Harrison R O, Young J W, Freeman A E and
Ford S P 1989 Effects of lactational level on reactivation of
ovarian function, and interval from parturition to first visual
estrous and conception in high.producing Holstein cows. Animal
Production 49:23.28

Jainudeen M R 1985 Reproduction in
draught animals: Does work affect female fertility. In: Draught
Animal Power for Production (Editor: J W Copland). Proceedings of
an International Workshop held at James Cook University,
Townsville, Qld, Australia, July 10.16, pp130.133

Khibe P and Bartholomew P 1993 Dry
season feed supplementation for work oxen in the semi.arid zone
of sub.sahelian Africa. In Research for Development of Animal
Traction (Editors: Lawrence and Dijkman), The proceedings of the
4th Workshop of the West African Animal Traction Network, held
4.9 July 1990 in Kano, Nigeria. International Livestock Centre
for Africa, Addis Ababa, Ethiopia

Lawrence P and Zerbini E 1993 Recent
trends in research on draught animal nutrition. Paper presented
at the first workshop on Human and Draught Animal Power in crop
Production: Experiences, Present Status and Research Priorities.
January 19.22, 1993. Harare, Zimbabwe

MAFF 1984 Energy allowances and feeding
systems for ruminants. Reference Book 433. Ministry of
Agriculture, Fisheries and Food. HMSO. London

Mathers J C and Otchere E O 1993 Research
on nutrition of working animals: needs, experiences and methods.
In Research for Development of Animal Traction (Editors: Lawrence
and Dijkman), The proceedings of the 4th Workshop of the West
African Animal Traction Network, held 4.9 July 1990 in Kano,
Nigeria. International Livestock Centre for Africa, Addis Ababa,
Ethiopia (in press)

Matthewman R W, Dijkman J T and Zerbini E
1990 The management and husbandry of male and female draught
animals: Research achievements and needs. Paper presented at the
fourth Workshop of the West African Animal Traction Network
entitled "Research for Development on Animal Traction in
West Africa" held on 9.13th July 1990, in Kano, Nigeria